optimizeCompareInstr - Convert the instruction to set the zero flag so that we can remove a "comparison with zero"; Remove a redundant CMP instruction if the flags can be updated in the same way by an earlier instruction such as SUB. More...

The commutable operands are specified by their indices OpIdx1 and OpIdx2.

Do not call this method for a non-commutable instruction or for non-commutable pair of operand indices OpIdx1 and OpIdx2. Even though the instruction is commutable, the method may still fail to commute the operands, null pointer is returned in such cases.

optimizeCompareInstr - Convert the instruction to set the zero flag so that we can remove a "comparison with zero"; Remove a redundant CMP instruction if the flags can be updated in the same way by an earlier instruction such as SUB.

optimizeCompareInstr - Convert the instruction supplying the argument to the comparison into one that sets the zero bit in the flags register; Remove a redundant Compare instruction if an earlier instruction can set the flags in the same way as Compare.

E.g. SUBrr(r1,r2) and CMPrr(r1,r2). We also handle the case where two operands are swapped: SUBrr(r1,r2) and CMPrr(r2,r1), by updating the condition code of instructions which use the flags.

shouldScheduleLoadsNear - This is a used by the pre-regalloc scheduler to determine (in conjunction with areLoadsFromSameBasePtr) if two loads should be scheduled togther.

On some targets if two loads are loading from addresses in the same cache line, it's better if they are scheduled together. This function takes two integers that represent the load offsets from the common base address. It returns true if it decides it's desirable to schedule the two loads together. "NumLoads" is the number of loads that have already been scheduled after Load1.

On some targets if two loads are loading from addresses in the same cache line, it's better if they are scheduled together. This function takes two integers that represent the load offsets from the common base address. It returns true if it decides it's desirable to schedule the two loads together. "NumLoads" is the number of loads that have already been scheduled after Load1.

FIXME: remove this in favor of the MachineInstr interface once pre-RA-sched is permanently disabled.